Photographic developer and method of developing latent images



UNITED $1"Ares PATENT omen.

ALONZO S. MGDANIEL, 01' YORK, AND ADOLPIH H. NIETZ, OF ROCHESTER, NEW

YORK, ASSIGNOB/S TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A I

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Io Drawing. Application filed April 10, 1917, Serial No. 181,019. lenewed september 4, 1920. Serial.

Specification of Letters Patent.

Patented Mar. 8, 1921.

To all whom it may concern:

Be it known that we, ALONZO S. MGDAN- IEL and ADOLPH H. Nm'rz, residing in New York, county of New York, State of New York, and in Rochester, county of Monroe,

State .of New York, respectively, have 'in-= vented new. and useful Improvements in 'Photographic Developers and Methods of Developing Latent Images, of which the following is a specification.

Our invention relates to hotographic developers and a method of eveloping latent images and has for an object the provision of a developing agent for photographic images which possesses a re uction potential especially suitable for-underexposed sensitive elements. To this and other ends, which will appear hereinafter in the following disclosure, our invention resides in the subject matter set forth in the claims appended hereto.

In the development of photographic images, it is considered that part of the grains 0 the photographic sensitive material often remain untouched by various types of developers, so that not all of the latent image that can be developed has been brought out by this treatment. We have discovered that diaminophenol sulfonic acid has the remarkable propert ofdeveloping more of the latent image t an heretofore obtainable by the ordinary developers, when the latent image has been produced by a short time underexposure or the usual out-of-doors snapshot. If, for example in ordinary instantaneous photography, a photographic film has been subjected to too weaka light and the image produced by the usual well known developers and methods of development is faint and flat, the resulting negative will be practically valueless for positive printing'pu oses. By treating such an underexposed l i developing bath, it is possible to obtain an image of considerable contrast and with better rinting qualities than heretofore ob-' tainab e, so that many underexposed negatives may be preserved and reasonably satisfactory prints made therefronn In the practice of our. invention, it is our purpose to employ as the developing agent the chemical compound known as diammo- A suitable 1m to the action of our phenol sulfonic acid having th e following structural formula con H on

agent may e made up asfollowsz Diaminophenol sulfonic acid.-- 40 grams.

While the above specified proportions are satisfactory for one type of sensitive element, it is to be understood that the bath may be varied within wide limits subject to the limi'tin conditions which. determine the qualit an character of the resulting Iproduct. n accordance therewith, it sho d be noted that the sulfite should be. sufliciently h1gh in concentratlon to prevent a too rapid oxidationof the developer. Furthermore, the addition of carbonate increases the speed of development, the density-giving power andthe reduct1on potential of the developerto a llmlted extent u to a point where a general fog is obtaine by the presence 0 too much carbonate. A bath containing diaminophenol sul'fonic acid works without the alkali or carbonate, although more slowly. Howphotographic bath involving this I resent in the bath;

In the operation of our process, a photo- Y graphic element bearing for example a 'silver salt emulsion which has been exposed to light may have its latent image develo into a .visible image byimmersion or ot er treatment in a bath made up in accordance with the above formula for such a len h of time as is necessary to bring out a visi le image, in accordance with well'known principles of photographic procedure. The element may then be washed and the image fixed in hypo and again washed orthe same may be otherwise treated in accordance with usual or desirable methods. After the element has been dried, a photographic element bearin the desired image is had, which may be preserved for various purposes.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A photographic developer'comprising an alkaline solution containing diaminophenol sulfonic acid. I

2. A photographic developer comprising diaminophenol sulfonic acid, an alkali sulfite and an alkali carbonate.

3. A photographic developer-comprising an aqueous solution containing diaminophenol sulfonic acid, sodium sulfite, sodium carbonate and potassium bromid. v

4. The process of developing a photo? graphically sensitive element exposed to actinic light, comprising the step of treating said element with an aqueous solution containin diaminophenol sulfonic acid.

5. he process of developing a photographically sensitive element exposed to actinic light, comprising the step of treating said element with an aqueous solution containing diaminophenol sulfonic acid, sodium sulfite, sodium carbonate and potassium bromid.

In testimony whereof, we have signed this specificatlon in the presence of two witnesses this 5th da of April, 1917.

ALONZ S. McDANIEL. ADOLPH H. NIETZ. 'Witnesses:

GEORGE COURTNEY CooKE,

C. E. MARTIN. 

